This invention relates to compounds suitable for use as dyes, to inks and to their use in ink jet printing (xe2x80x9cIJPxe2x80x9d). IJP is a non-impact printing technique in which droplets of ink are ejected through a fine nozzle onto a substrate without bringing the nozzle into contact with the substrate.
There are many demanding performance requirements for dyes and inks used in IJP. For example they desirably provide sharp, non-feathered images having good water-fastness, light-fastness and optical density. The inks are often required to dry quickly when applied to a substrate to prevent smudging, but they should not form a crust over the tip of an ink jet nozzle because this will stop the printer from working. The inks should also be stable to storage over time without decomposing or forming a precipitate which could block the fine nozzle.
According to the present invention there is provided a compound of Formula (1) and salts thereof: 
wherein:
A is optionally substituted phenyl;
R1 and R2 are each independently optionally substituted alkyl or optionally substituted alkoxy; and
R4 and R5 are each independently H, optionally substituted alkyl or optionally substituted aryl; provided that: (i) at least one of R1 and R2 carries an xe2x80x94OH group; and
(ii) A is not of the formula: 
wherein m is 1, 2 or 3.
Preferably A is phenyl carrying one or two substituents.
The optional substituents which may be present on A are preferably selected from xe2x80x94OH; optionally substituted amino, especially xe2x80x94NH2; halo, especially Cl, Br and F; ester, especially xe2x80x94CO2xe2x80x94C1-4-alkyl; xe2x80x94CN; xe2x80x94NO2; optionally substituted alkyl; optionally substituted alkoxy; xe2x80x94CO2H; xe2x80x94SO3H; xe2x80x94SO2NR3R3; xe2x80x94OR3; or xe2x80x94SR3; wherein each R3 independently is H or C1-4-alkyl. Especially preferred optional substituents for A are selected from optionally substituted C1-4-alkyl and optionally substituted C1-4-alkoxy, the preferred optional substituents being selected from carboxylic acid, sulphonic acid and phosphoric acid.
R1 and R2 are preferably each independently optionally substituted C1-4-alkyl or C1-4-alkoxy, more preferably optionally substituted C1-4-alkoxy, provided that at least one of R1 and R2 carries an xe2x80x94OH group. The optional substituents which may be present on R1, R2, R4 and R5 are preferably selected from xe2x80x94NH2; halo, especially Cl, Br and F; ester, especially xe2x80x94CO2xe2x80x94C1-4-alkyl; xe2x80x94Oxe2x80x94C1-4-alkyl; xe2x80x94CO2H; xe2x80x94SO3H; xe2x80x94OR3; or xe2x80x94SR3; wherein each R3 independently is H or C1-4-alkyl, provided that at least one of R1 and R2 carries an xe2x80x94OH group.
Preferably both R1 and R2 carry an xe2x80x94OH group.
Preferably R4 and R5 are each independently H, optionally substituted C1-4-alkyl or optionally substituted phenyl, more preferably H, or C1-4-alkyl or phenyl carrying 1 or 2 groups selected from carboxy and sulpho. More preferably R4 and R5 are both H.
The compounds of Formula (1) may be prepared by diazotising a compound of the Formula (2) to give a diazonium salt and coupling the resultant diazonium salt with a 1-hydroxy-3-sulpho-7-aminonaphthalene: 
wherein A, R1 and R2 are as hereinbefore defined.
The hydroxy group(s) on R1 and/or R2 may be protected during the diazotisation, for example using an acid labile or base labile protecting group. The acetoxy protecting group is particularly convenient and inexpensive.
The diazotisation is preferably performed at a temperature below 6xc2x0 C., more preferably at a temperature in the range xe2x88x9210xc2x0 C. to 5xc2x0 C. Preferably the diazotisation is performed in water, preferably at a pH below 7. Dilute mineral acid, e.g. HCl or H2SO4, may be used to achieve the desired acidic conditions.
The compound of Formula (2) may be prepared by diazotising a compound of formula Axe2x80x94NH2 and coupling onto an aniline compound carrying R1 and R2 groups at the 2- and 5-positions respectively, wherein A, R1 and R2 are as hereinbefore defined.
Preferred salts are alkali metal salts (especially lithium, sodium and potassium salts), ammonium and substituted ammonium salts and mixtures thereof. Especially preferred salts are sodium, potassium and lithium salts, salts with ammonia and volatile amines and mixture thereof. The lithium salts have good solubility, forming particularly storage stable inks with low toxicity and low tendency to block ink jet nozzles.
The compounds may be converted into a desired salt using known techniques. For example, an alkali metal salt of a compound may be converted into the ammonium or substituted ammonia salt by dissolving an alkali metal salt of the dye in water, acidifying with a mineral acid and adjusting the pH of the solution to pH 9 to 9.5 with ammonia or the amine and removing the alkali metal cations by dialysis or by use of an ion exchange resin.
Examples of amines which may be used to form such salts include methylamine, dimethylamine, trimethylamine, ethylamine, n-propylamine, iso-propylamine, n-butylamine, iso-butylamine, sec-butylamine, tert-butylamine, piperidine, pyridine, morpholine, allylamine, diethylamine, triethylamine, tetramethylamine and mixtures thereof. It is not essential that the dyes are completely in the form of the ammonium salt or substituted ammonium salt and mixed alkali metal and either ammonium salt or substituted ammonium salt are effective, especially those in which at least 50% of the cations are ammonium or substituted ammonium ions.
Still further salts are those with the counter ions described in U.S. Pat. No. 5,830,265, claim 1, integer (b), which are included herein by reference thereto.
The compounds of Formula (1) may exist in tautomeric forms other than those shown in this specification. These tautomers are included within the scope of the present claims.
According to a second aspect of the present invention there is provided an ink comprising a compound of Formula (1) or salt thereof and a liquid medium or a low melting point solid medium.
A preferred ink comprises:
(a) from 0.01 to 30 parts of a compound of the Formula (1) or salt thereof; and
(b) from 70 to 99.99 parts of a liquid medium or a low melting point solid medium; wherein all parts are by weight and the number of parts of (a)+(b)=100.
The number of parts of component (a) is preferably from 0.1 to 20, more preferably from 0.5 to 15, and especially from 1 to 5 parts. The number of parts of component (b) is preferably from 99.9 to 80, more preferably from 99.5 to 85, especially from 99 to 95 parts.
When the medium is a liquid, preferably component (a) is completely dissolved in component (b). Preferably component (a) has a solubility in component (b) at 20xc2x0 C. of at least 10%. This allows the preparation of liquid dye concentrates which may be used as an ink or to prepare inks and reduces the chance of the dye precipitating if evaporation of the liquid medium occurs during storage.
Preferred liquid media include water, a mixture of water and an organic solvent and an organic solvent free from water.
When the liquid medium comprises a mixture of water and an organic solvent, the weight ratio of water to organic solvent is preferably from 99:1 to 1:99, more preferably from 99:1 to 50:50 and especially from 95:5 to 80:20.
It is preferred that the organic solvent present in the mixture of water and organic solvent is a water-miscible organic solvent or a mixture of such solvents. Preferred water-miscible organic solvents include C1-4-alkanols, preferably methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, n-pentanol, cyclopentanol and cyclohexanol; linear amides, preferably dimethylformamide or dimethylacetamide; ketones and ketone-alcohols, preferably acetone, methyl ether ketone, cyclohexanone and diacetone alcohol; water-miscible ethers, preferably tetrahydrofuran and dioxane; diols, preferably diols having from 2 to 12 carbon atoms, for example pentane-1,5-diol, ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol and thiodiglycol and oligo- and poly-alkyleneglycols, preferably diethylene glycol, triethylene glycol, polyethylene glycol and polypropylene glycol; triols, preferably glycerol and 1,2,6-hexanetriol; mono-C1-4-alkyl ethers of diols, preferably mono-C1-4-alkyl ethers of diols having 2 to 12 carbon atoms, especially 2-methoxyethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)-ethanol, 2-[2-(2-methoxyethoxy)ethoxy]ethanol, 2-[2-(2-ethoxyethoxy)-ethoxy]-ethanol and ethyleneglycol monoallylether; cyclic amides, preferably 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, caprolactam and 1,3-dimethylimidazolidone; cyclic esters, preferably caprolactone; sulphoxides, preferably dimethyl sulphoxide and sulpholane. Preferably the liquid medium comprises water and 2 or more, especially from 2 to 8, water-soluble organic solvents.
Especially preferred water-soluble organic solvents are cyclic amides, especially 2-pyrrolidone, N-methyl-pyrrolidone and N-ethyl-pyrrolidone; diols, especially 1,5-pentane diol, ethyleneglycol, thiodiglycol, diethyleneglycol and triethyleneglycol; and mono-C1-4-alkyl and C1-4-alkyl ethers of diols, more preferably mono-C1-4-alkyl ethers of diols having 2 to 12 carbon atoms, especially ((2-methoxy)-2-ethoxy)-2-ethoxyethanol.
Examples of further suitable ink media comprising a mixture of water and one or more organic solvents are described in U.S. Pat. No. 4,963,189, U.S. Pat. No. 4,703,113, U.S. Pat. No. 4,626,284 and EP 4,251,50A.
When the liquid medium comprises an organic solvent free from water, (i.e. less than 1% water by weight) the solvent preferably has a boiling point of from 30xc2x0 to 200xc2x0 C., more preferably of from 40xc2x0 to 150xc2x0 C., especially from 50 to 125xc2x0 C. The organic solvent may be water-immiscible, water-miscible or a mixture of such solvents. Preferred water-miscible organic solvents are any of the hereinbefore described water-miscible organic solvents and mixtures thereof. Preferred water-immiscible solvents include, for example, aliphatic hydrocarbons; esters, preferably ethyl acetate; chlorinated hydrocarbons, preferably CH2Cl2; and ethers, preferably diethyl ether; and mixtures thereof.
When the liquid medium comprises a water-immiscible organic solvent, preferably a polar solvent is included because this enhances solubility of the compound in the liquid medium. Examples of polar solvents include C1-4alcohols. In view of the foregoing preferences it is especially preferred that where the liquid medium is an organic solvent free from water it comprises a ketone (especially methyl ethyl ketone) and/or an alcohol (especially a C1-4-alkanol, more especially ethanol or propanol).
The organic solvent free from water may be a single organic solvent or a mixture of two or more organic solvents. It is preferred that when the medium is an organic solvent free from water it is a mixture of 2 to 5 different organic solvents. This allows a medium to be selected which gives good control over the drying characteristics and storage stability of the ink.
Ink media comprising an organic solvent free from water are particularly useful where fast drying times are required and particularly when printing onto hydrophobic and non-absorbent substrates, for example plastics, metal and glass.
Preferred low melting solid media have a melting point in the range from 60xc2x0 C. to 125xc2x0 C. Suitable low melting point solids include long chain fatty acids or alcohols, preferably those with C18-24 chains, and sulphonamides. The compound of Formula (1) may be dissolved in the low melting point solid or may be finely dispersed in it.
The compounds of the invention may be used as the sole colorant in inks because of their attractive black shade. However, if desired, one may combine the compounds with one or more further colorants if a slightly different shade is required for a particular end use. The further colorants are preferably dyes. When further colorants are included in the ink these are preferably selected from black, cyan and yellow colorants and combinations thereof.
Preferred black colorants include C.I.Food Black 2, C.I.Direct Black 19, C.I.Reactive Black 31, PRO-JET Fast Black 2, C.I.Direct Black 195; C.I.Direct Black 168; and black dyes described in patents by Lexmark (e.g. EP 0 539,178 A2, Example 1, 2, 3, 4 and 5), Orient Chemicals (e.g. EP 0 347 803 A2, pages 5-6, azo dyes 3, 4, 5, 6, 7, 8, 12, 13, 14,15 and 16) and Seiko Epson Corporation.
Preferred cyan colorants include C.I.Direct Blue 199; C.I.Acid Blue 9; C.I.Direct Blue 307; C.I.Reactive Blue 71; and C.I.Direct Blue 85.
Preferred yellow colorants include C.I.Direct Yellow 142; C.I.Direct Yellow 132; C.I.Direct Yellow 86; C.I.Direct Yellow 85; and C.I.Acid Yellow 23.
However, as mentioned above, it is not normally necessary to use further colorants in conjunction with compounds of the present invention.
The ink may also contain additional components conventionally used in ink jet printing inks, for example viscosity and surface tension modifiers, corrosion inhibitors, biocides, kogation reducing additives and surfactants which may be ionic or non-ionic.
A further aspect of the invention provides a process for printing an image on a substrate comprising applying an ink containing a compound of Formula (1) to the substrate by means of an ink jet printer.
The ink used in this process is preferably as defined in the second aspect of the present invention.
The ink jet printer preferably applies the ink to the substrate in the form of droplets which are ejected through a small orifice onto the substrate. Preferred ink jet printers are piezoelectric ink jet printers and thermal ink jet printers. In thermal ink jet printers, programmed pulses of heat are applied to the ink in a reservoir by means of a resistor adjacent to the orifice, thereby causing the ink to be ejected in the form of small droplets directed towards the substrate during relative movement between the substrate and the orifice. In piezoelectric ink jet printers the oscillation of a small crystal causes ejection of the ink from the orifice.
The substrate is preferably paper, plastic, a textile, metal or glass, more preferably paper, an overhead projector slide or a textile material, especially paper.
Preferred papers are plain or treated papers which may have an acid, alkaline or neutral character.
Preferred papers are plain or treated papers which may have an acid, alkaline or neutral character. Examples of commercially available treated papers include HP Premium Coated Paper (available from Hewlett Packard Inc), HP Photopaper (available from Hewlett Packard Inc), Stylus Pro 720 dpi Coated Paper, Epson Photo Quality Glossy Film (available from Seiko Epson Corp.), Epson Photo Quality Glossy Paper (available from Seiko Epson Corp.), Canon HR 101 High Resolution Paper (available from Canon), Canon GP 201 Glossy Paper (available from Canon), and Canon HG 101 and HG201 High Gloss Film (available from Canon).
A further aspect of the present invention provides a paper, an overhead projector slide or a textile material printed with an ink, a compound or by means of a printing process as hereinbefore defined.
A still further as aspect of the present invention provides an ink jet printer cartridge, optionally refillable, containing an ink according to the second aspect of the present invention.
The compounds and inks of the invention have attractive, neutral black shades and are particularly well suited for the ink jet printing of text and images. The inks have good storage stability and low tendency to block the very fine nozzles used in ink jet printers. Furthermore, the resultant images have good optical density, light-fastness, wet-fastness and resistance to fading in the presence of oxidising air pollutants.